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Biochemistry- Paper-2


Q.N.1. –a) Describe the essential differences between Metabolic Acidosis and Respiratory Acidosis.  

 b) Discuss the role of Renin -Angiotensin system in the maintenance of water and electrolyte balance of the body.

Q.N. 2. – a) What is PCR? Describe in detail the steps and applications of PCR.                                                  

b)Give a brief description of the Lac operon model of Gene expression.                                                           

Q.N.3. – a) Describe the various tests which are based on excretory functions of liver.                                     

b) Define Detoxification, Why is it required? Describe the various types of detoxification reactions occurring in the body giving one suitable example of each reaction.                                                                                                                 

Q.N.4- Write short notes on-                                                                                                                                                        

a)  Thin layer Chromatography

b) Balanced diet

c) Post translational modifications

Q.N.5 – a) What is BMR? Discuss the role of various factors that affect the BMR.                                               

b) Explain briefly the transmission and the natural course of AIDS.                                                                               

Q.N.6- Describe the followings-                                                                                                                                         

a) Characteristics of Genetic code

b) Etiology of cancers

c) Orotic aciduria

d) Sparing action



(Multiple choice questions)

Date-   04-11-08-08                                                                                                                                    

Q.N.1- – The function of the Topo Isomerases is-                                          

a)  Proof reading                                                         b) Relief of super coils

c)  Polymerization                                                       d) clamp loading.

Q.N.2- Actinomycin D is an inhibitor of-                                                      

a) Replication                                                              b) Transcription

c) Translation                                                              d) all of the above.

 Q.N.3- The HIV genome can be identified by the following test:-         

a) ELISA                                                                    b) Western blot

c) PCR                                                                        d) any one of the above

 Q.N.4- In phenyl ketonurics, the phenyl acetic acid is conjugated by-    

a) Glycine                                                                 b) Acetylation

c) Glutamine                                                           d) Methylation

 Q.N.5- On the third day, following the onset of Acute Myocardial infarction which enzyme estimation will have the best predictive value?                                                                                                         

a) Serum AST                                                             b) Serum ALT

c) Serum CPK                                                             d) Serum LDH

 Q.N.6-Normal maximum Urea clearance (Cm) in an adult averages about-

a) 60                                                                            b) 65

c) 70                                                                            d) 75

 Q.N.7- The Prothrombin time in obstructive jaundice is                                

a) Normal                                                                    b) Low

c) Increases after injection of Vitamin K       d) none of the above.

 Q.N.8-   In which of the following enzymes, zinc constitutes an integral part of the enzyme-                                                                                      

a) Pepsin                                                                      b) Trypsin

c) Carbonic Anhydrase                                          d) Xanthine Oxidase  

Q.N. 9- Which of the following essential dietary factors is a precursor for a compound that acts as a “one carbon carrier”-                                                                                                                                                                               

a) Methionine                                                            b) Folic acid

c) Biotin                                                                      d) Thiamine

Q.N.10- The intake of which food stuff results in the greatest SDA-           

a) Carbohydrates                                                       b) Fats

c) Proteins                                                                   d) Calcium

Q.N.11- AFP is the most specific tumor marker for the primary carcinoma of the- 

a) Bone                                                                        b) Liver

c) Lungs                                                                      d) all of the above.                     

Q.N.12- Oxidation of which substance in the body yields the most calories per gram-

a) Glucose                                                                   b) Lipids

c) Animal protein                                                    d) Plant protein.          

Q.N.13- The synthesis of Adenylyl Cyclase is increased by-                                                  

a) Calcitonin                                                                b) Insulin

c) Parathormone                                                      d) Glucagon               

Q.N.14- RNA does not contain –                                                                                              

a) Uracil                                                                      b) Adenine

c) Thymine                                                                 d) Ribose.                    

Q.N.15- All are inhibitors of protein synthesis except-                                    

a) Tetra cyclin                                                             b) Erythromycin

c) Puromycin                                                               d) Streptoglidigin       

                                                     State true or false

Q.N.16- A given codon designates only one single specific amino acid.      

 Q.N.17-If a given Purine is changed to another Purine it is Transversion.    

 Q.N.18- The renal plasma flow is measured by the Hippuric acid test.       

 Q.N.19- Sudden increase in Gamma Glutamyl Transferase enzyme in Chronic Alcoholics signifies recent bout of drinking of Alcohol.                                                                                                                                  

 Q.N.20- The Atrial Natriuretic Peptide Hormone is synthesized in the adrenal cortex.                                                                                                                                                                                                                                                                  

                                                           Model Answers

Q.N.1- Multiple choice questions.


2) b

3) d

4) c

5) d

6) d

7) c

8) c

9) b

10) c

11) b

12) b

13) d

14) c

15) d

16) True

17) False

18) False

19) True

20) False


Q.N.2-a)  The differences between Metabolic acidosis and Respiratory Acidosis- Metabolic acidosis is primary alkali deficit due to the deficiency of bicarbonate ions, While Respiratory Acidosis is due to primary carbonic acid excess. The p H and the ratio is altered in both the cases but the causes and the compensatory mechanisms and the treatment are different in both the cases. All the causes, compensatory mechanisms and the treatment are to be discussed in the tabular manner.

b) Renin – Angiotensin system- Renin is a proteoltic enzyme released from the kidney. It is released in response to the fall in sodium ion concentration, Hypovolemia, hypotension and a fall in intra cellular calcium ion conc., All these factors  stimulate the release of Renin from J.G. cells to blood. The action of Renin is mediated through the release of Angiotensin I from Angiotensinogen. Angiotensin I  is then converted to Angiotensin II and then to Angiotensin III. Both the later Angiotensins cause the release of Aldosteron from the Adrenal cortex, which causes the absorption of Sodium ions to restore the blood pressure and the fluid volume. The interdependence of Renin- Angiotensin system and the Aldosterone are  to be discussed. The clinical significance and the use of ACE inhibitors for the treatment of Hypertension are to be discussed.

Q.N.2-a)  PCR- Polymerase chain reaction is a method of amplifying a target sequence of DNA. The flanking sequences of the target DNA are required to be known. Two primers  of about 20-30 nucleotides with complementary sequence of the flanking region can be synthesized. DNA strands are separated by heating at 95 degree centigrade for 15 seconds to 2 minutes. The primers are annealed by cooling to 50 degree centigrade. The primers hybridize with their complementary single stranded DNA produced in the first step. New strands are synthesized by Taq. Polymerase. The enzyme is heat resistant , hence  it is not denatured at that high temperature. The polymerase reaction is allowed to take place for 30 seconds in the presence dNTPs. Both strands of DNA are thus duplicated. The steps are repeated, in each cycle the DNA strands are duplicated. Thus in a short span of time by simple technique the DNA  is amplified many times. In reverse PCR m RNA is detected , this allows c DNA synthesis from m RNA, followed by PCR amplification. The PCR technique is used for the diagnosis of various diseases, for medico legal cases, for the diagnosis of genetic disorders, cancer detection and also for the  Paleontological studies to study the evolution of life. The diagram showing the steps is needed.

b) Lac operon model- The synthesis of proteins under the influence of genes is called gene expression. All the genes of the cell are not expressed at all the  time. The Lac operon is an inducible catabolic operon of E.Coli. It consists of structural genes and the regulatory genes. The structural genes Z,Y and A transcribe to form a single large m-RNA with three independent translational units for the synthesis of three  distinct enzymes. The regulatory genes produce the Repressor molecule , the expression of which is constitutive. The repressor has a strong affinity for the operator which is the site between the promoter and the structural genes. When the repressor is attached to the operator the RNAP can not move further and thus the transcription of the structural genes is inhibited. So the structural genes are not transcribed. Thus when the lactose is not available, the lactose utilizing enzymes are not synthesized. When lactose is there in the medium the it binds to the repressor molecule and this complex becomes inactive and can no longer bind to the DNA. Thus the structural genes are  transcribed and the lactose is thereby utilized.

 The  Repression, De-repression of the lac operon are  to be discussed. The role of cAMP  is also to be discussed.

Q.N.3- a) Tests based on the excretory functions of the liver-  Bilirubin is formed by the catabolism of heme .It is the excretory product formed in the liver. It is conjugated in the liver to form the Bilirubin diglucuronide and excreted through bile. Measurement of Serum Biliribin, urobilinogen and stercobilinogen in blood and urine are important tests of liver functions. Besides that the BSP retention test and Indocyanin Green tests are to be discussed.

 Reactions of conjugation of Bilirubin are to be discussed with clinical significance.

 b) Detoxification- The biochemical processes whereby the toxic substances are rendered nontoxic and more water soluble are termed as detoxification. The toxicants that are lipophilic, non-polar and  are of low molecular weight are readily absorbed through the cell membranes of the skin, GI Tract and lungs and accumulate in the lipid rich areas to produce the toxic effects.  By Detoxication the substances are processed through two phases Phase I reactions are hydroxylation reactions , while phase II reactions are conjugation reactions.

 Details with  one example each are to be given for both the phases, concluding with the harmful effects of xenobiotics if they are not rendered non toxic.

 Q.N.4- a)Thin Layer Chromatography- This is another version of the liquid- liquid chromatography. A thin layer of the silica gel is spread on a glass plate, biological sample is applied as a small spot .The plate is placed in a trough containing the solvent. The stationary water phase is held on the silica gel and the mobile phase of non polar solvent moves up. In the case of TLC it takes only 3-4 hours for the separation of the substances in comparison to Paper chromatography which takes 14-16 hours, that is a distinct advantage for TLC.

Diagram, indications , merits , demerits are to be discussed.

b) Balanced Diet- A diet is said to be a balanced one when it includes proportionate quantities of food items selected from the different basic food groups so as to supply the essential nutrients in the complete fulfillment of the requirement of the body. The basic food groups and the criteria for the planning of a balanced diet are to be discussed.

c) Post Translational Modifications- The mature functional protein is formed by the post translational processes, which include the following processes-

1) Proteolytic cleavage

2) Modification of the amino acids

3) Sub unit aggregation etc. are to be discussed with suitable examples.

Q.N.5-a) BMR- The basal metabolic rate may be defined as the energy required by an awake individual during physical, emotional and digestive rest. It is the minimum amount of energy required to maintain life or sustain vital functions like the working of the heart, circulation, brain functions, respiration etc. The measurement of BMR in brief is to be discussed along with the elaboration of various factors that produce variations in BMR

 The significance of measurement is also to be discussed.

b) Transmission of HIV- The various routs like the blood, placenta ,sex etc are to me mentioned.

Natural course of the disease- Window period, seropositiveness stage and the phase of full blown AIDS are to be discussed.

Q.N.6-a) Characteristics of the Genetic code- The salient features like-

Triplet codon, non overlapping, non punctuated, degenerate, unambiguous and universal characteristics etc are to be discussed.

b) Etiology of Cancers- All cancers are multifactorial in origin. They include  genetic, hormonal, metabolic, physical, chemical and environmental factors. The effect of mutations and chemical carcinogens is also to be discussed.

c) Orotic aciduria- This condition results from the absence of either or both of the enzymes-OPRTase or OMPdecarboxylase. S/s, the lab.diagnosis and the treatment are  to be discussed.

d) Sparing action- The examples of formation of Tyrosine from phenyl Alanine and the formation of carbohydrates from the c- skeleton of amino acids is to be discussed. The relative decrease in the requirement of the phenyl Alanine and proteins is to be discussed in brief.



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